Measurement, Source-Profiling and Potential Toxicity of Polycyclic Aromatic Hydrocarbons in an Agrarian Soil

The study focused on polycyclic aromatic hydrocarbons (PAHs) in the surface soil of an acquired agricultural land with the aim of understanding their sources and possible toxicity. Eight (8) composite samples were taken in February 2019, and the PAHs were extracted by ultrasonic treatment, followed by chromatographic purification. The PAHs included the 16 USEPA priority PAHs and six others. They were analyzed using a gas chromatograph-mass spectrometer (GC-MS). The average concentration of the 22 PAHs was 33.0 mu g/g. The concentration of DiBahA was exceptionally high at 6.32 mu g/g. Among the PAHs, 4-6 rings PAHs were dominant, constituting 75%. The average concentrations of the priority and 8 IARC-carcinogenic PAHs were 30.1 and 16.1 mu g/g, respectively. Both diagnostic ratio and positive matrix factorization (PMF) confirmed that the PAHs were of pyrogenic sources. Fifty-three percent (53%) of the total PAHs were due to fuel combustion of engines, while coal and biomass burning accounted for 47%. Assessment of the potential eco-toxicity and toxicity to human health showed that the priority PAHs constitute high ecological and human health risk, of which the 8 carcinogenic PAHs were main contributors to the total toxicity (7.54 mu g BaPeq g(-1)). DiBahA and BaP accounted for 84% and 9.3% toxicity of the carcinogenic PAHs, respectively. This implies heavy contamination of the surface soil, and thus confirmed soil as the most important sink for PAHs in the environment.